java.lang.Object；无法转换到购物篮。产品

Question

我正在尝试检索产品列表及其相关优惠。迭代查询结果后，我希望能够使用产品类中的 getter/setter，但我知道它不起作用，因为查询没有返回 Product 的实例。

抓取产品功能:

public List<Product> getProducts() {
    factory = (new Configuration()).configure().buildSessionFactory();
    Session session = factory.getCurrentSession();

    session.beginTransaction();

    List<Product> products = new ArrayList<Product>();

    Query query = session.createQuery("from Product p INNER JOIN p.offers"); 
    //The castList is declared and explained at the bottom of listing
    List<Product> list =  query.list();

    Iterator<Product> iter = list.iterator();

    while (iter.hasNext()) {
        Product product = iter.next();
        System.out.println(product);
    }
}

Offer 的 Hibernate 映射:

<hibernate-mapping>
<class name="shoppingbasket.Offer" table="offers">
    <id name="offerID" type="integer" access="field">
        <column name="OfferID" />
        <generator class="assigned" />
    </id>
    <property name="offerDescription" type="java.lang.String" access="field">
        <column name="OfferDescription" length="60" not-null="true"/>
    </property>
    <property name="shortDescription" type="java.lang.String" access="field">
        <column name="ShortDescription" length="10" not-null="false"/>
    </property>
    <property name="TFTPOTGroup" type="java.lang.Integer" access="field">
        <column name="TFTPOTGroup" length="4" not-null="false" default="null"/>
    </property>
    <property name="discountPercentage" type="java.lang.Double" access="field">
        <column name="DiscountPercentage"  not-null="false" default="null"/>
    </property>
</class>

产品的 Hibernate 映射:

<hibernate-mapping>
<class name="shoppingbasket.Product" table="products">
    <id name="productID" type="integer" access="field">
        <column name="ProductID" />
        <generator class="assigned" />
    </id>
    <property name="offerID" type="java.lang.Integer" access="field">
        <column name="OfferID" />
    </property>
    <property name="productName" type="java.lang.String" access="field">
        <column name="ProductName" length="40" not-null="true"/>
    </property>
    <property name="unitPrice" type="java.math.BigDecimal" access="field">
        <column name="UnitPrice"/>
    </property>
    <one-to-one name="offers" class="shoppingbasket.Offer" />
</class>

产品类别:

public class Product implements java.io.Serializable {
private Integer productID;
private Integer offerID;
private String productName;
private BigDecimal unitPrice;
private Offer offer;
public Integer getProductID() {
    return productID;
}
public void setProductID(Integer productID) {
    this.productID = productID;
}
public Integer getOfferID() {
    return this.offerID;
}
public void setOfferID(Integer offerID) {
    this.offerID = offerID;
}
public Offer getOffers() {
    return offer;
}
public void setOffers(Offer offer) {
    this.offer = offer;
}
//more getters/setters
}

优惠类别:

public class Offer
{
private Integer offerID;
private String offerDescription;
private String shortDescription;
private Integer TFTPOTGroup;
private Double discountPercentage;
public Integer getOfferID() {
    return offerID;
}
public void setOfferID(Integer offerID) {
    this.offerID = offerID;
}
//more getters/setters

}

任何帮助将不胜感激

Answer 1

#潜在不必要的预测数据:

由于您没有在查询中指定 SELECT 子句并放置显式联接，hibernate 将每行返回 2 个对象(产品、优惠)，其中由于底层映射关联，Product 对象可能已经填充了 Offer 数据。

尝试将 select 子句添加到查询中，看看它是否正确转换

Add SELECT p FROM ... to the query